Pressure / Leak Testing A Two-Stroke Engine & Building A Tester 2T 

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When all else fails submerge the test underwater completely, I've had some 2stroke engines (and even tires when i worked at a tire shop) that had leaks that didn't want to make soapy water bubble up.

Thanks for the years of great content!

Cannot thank you enough for such a brilliantly executed tutorial. Always familiar with carb pressure testing, but now because of your video, I understand whole engine pressure testing. Your personality delightful, and your choice of music with the time check section also top shelf. Blessings coupled with all the best from New Rochelle N.Y.

Absolutely by far one of the best videos I have watched on this subject! You covered all the basics that I needed to know. I am working on a chainsaw for a family member. Replaced the cylinder, piston and ring. Now starts but wont stay running. Suspect engine leak. Now I have options on how to find it! Thank you....Thank you....Thank you!!!!!

What a roller coaster of a task! Great video , glad it was all wrapped up within one video, really good quality stuff. Excited to get this all set up for myself to go through on my Dio. Having a pain tuning it and I'm suspecting an air leak. Wish I did this before I put it all back together and started tuning haha.

Good job with your description and procedures man! I built quite a few homemade leak testing contraptions over the years, I like how simple yours is.

Another great video. I throughly enjoy the more personal style lately and find it much more enjoyable to watch, aside from soaking up all the knowledge. This gentleman has been more helpful to me, than any other resource, by far. I came into the 2 stroke 1E40QMB world with some background knowledge from the 139qmb world and making plenty of mistakes there a few years ago and now, I feel like I have a somewhat comprehensive understanding of how a two stroke functions and have executed several somewhat complicated tasks. Between this channel and the 49ccscoot forum, we can all basically be Master Moped Mechanics haha.

That is probably the best vid on here explaining the test and how to build the rig. Absolutely brilliant content. Will subscribe to the Channel because of this vid!

You are the most thorough person I have ever seen doing a leak test on a 2 stroke. I rebuilt an engine that I am fighting idle issues with. I have found my large leak (intake manifold), but still leaking about 1 psi in 3 minutes. I have full confidence after watching this I will find it. Thank you for sharing your knowledge. Awesome video. I likely won't wait 30 minutes, but if it holds steady for 5 to 10 minutes like my manual says, I will be good with it.

Love the persistence. Great work bro

Thanks for a very thorough and informative video. Great work!

Greatest 2 stroke maintenenace video i ever saw

Brilliant - just what I was looking for as I suspect a leak on my engine. Thank you.

Great video. What I got importantly from this is---- test your test rig first before you take it near your engine, establishing a baseline for any pressure loss. Then go test your engine. I probably wouldn't have thought of that before viewing this so thanks for the upload, very comprehensive.

Thanks for taking the time to make this video! It helped a lot 🤙

You've taught me so much. Deepest thanks!

Fantastic video, very realistic of what to expect when doing the test yourself.

Very awesome and informative vid. I love the process of elimination and where to look for these culprit leaks. I’m also glad you were able to source a case halve and was able to match the porting, now you can get back to 2-stroke riding/testing vids! I need to split the case on my 1e40qmb and do bearings and seals, (might as well do crank too) this vid will help me go along to finish it off because of course you show your ways of not needing special tools for seal, crank installation. Will have to put a vid on the forum of the way these bearings sound! BTW Love the new Pure Pilot sport scoot tires with hi-vis color paint scheme! 🤙🏼

That’s what I call tight. Well done. Much appreciated...

Well done!

Thank you for this video it helped me, and I'm sure a lot of people. FYI You can probably take the back off of that guage then spray the mechanism, and also spray the intake for your pump to check its valves.

Hi, leakage from one way valve of your hand pump. This one way valve is weak and cannot keep high pressure more than blood pressure range. Thank you for this education.👍👏👌

Very good explanation. I use a evap smoke machine. Also you need to open the reeds to allow air to fill area on the carb side. I use a paper clip between the petal and seating surface of the cage.

Excellent video very informative thanks

Beautifully done. You really know how to make videos

Excellent video, enjoyed and learned from it. Exactly what I was looking for. A+ - - -thank you.

On a Skidoo 277cc shop manual it shows to pressurize to 5psi for 3 minutes so your test is very good

Nice to see you got youre groove again nince tutorial very thorough ps nice shirt!! Haha!!

brilliant video, thanks

Great video !

On the head gasket to see if it leaks I just run a compression test and make sure it don't fluctuate for several minutes or over night if you wish, I liked the video and didn't realize I had all them parts to make this leak down gauge.

Very informative, thx

Thanks for the vid - very informative

Thank you so much. Masterfully done, and I learned a lot. I have 2 chainsaws that are problematic. I will do my best to follow your example. I wish you health. Sincerely, Alicia from Sweden.

Wow! Nice video.Thanks for sharing.I learned alot.My suspicion would be the blood pressure bulb, or the check valve inside the bulb where the leak is.

Very awesome

Awesome Video Thx

Very good video!

Great Video To check for air loss in water jacket area(head gasket) put a rubber glove on the coolant ports gloves will fill with air

i did not realize you were a regular sized human ,now i do not feel so self aware about cruising my scoot's thanks

damn good job ! great tutorial- thanks. now i need to try to find a way to seal a 2 stroke outboard exhaust not typical/ a bit complicated.

👍👍👍👍 10,000 Times ! L O L relocated to a 3rd world country and Chinese motor cycle are everywhere, but trained machanic no where. Sooooo learning to do my own work. Again 10,000 👍👍👍👍.

Nice job Holmes

I put new crankseals in my Morini Franco 50cc, there was no movement on the gauge in a period of a few hours but it dropped about 1 PSI in about 24 hrs. I'm happy with that. My gauge is exactly the same as yours but I mounted it on a regular cylinder pressure tester after taking out the shrader valve and put a shrader valve from a tubless car tyre in the inlet port. The test on the rig that you done you could have submerged it in a tub of water just to cover the joints and looked for air bubbles. Great informative video though.

thanks a lot ! great video :D

Thank you so much.

Great video, made my plugs on a woodturning lath in oak and then fitted the brass fittings lol, all works : )

Superb..

I just wanna say make sure you look around the entire ports or entrances to wherever your spraying or checking which I'm sure you know that but ya know just throwing it out there some ppl are special 😁

Good job! Thanx for doing this video. Re-do the JB Weld or have it welded. Yes cheap gauges can be too cheap! Leaking, erratic readings. Do not use.

Fantastic vid bro always seemed a dark art thanks for your help👍 rich Somerset uk

nice video buddy.

best tutorials on youtube ! you should do mx bikes aswell

great. have some acceleration issues and terrible head ache on my scooter. I'll do this testing tomorrow fist thing.

This video was helpful…and somewhat comforting at the moment. I am going through a very similar situation right now. I did a leak test and found a crank seal was leaking, fixed it, but the gauge still shows a leak. I sprayed soapy water on every area where there could be a leak and saw ZERO bubbles. I actually did a few rounds of spraying everything with soapy water and still can’t find a leak. My tester is made up of the bulb and gauge from a blood pressure cuff, the tubing from a stethoscope, and one of the pieces from my compression test kit (to screw into the spark plug hole in the cylinder head). I used a similar setup before and it worked perfectly. I am crossing my fingers that it is just a bad gauge (even though it is brand new). I ordered components to make a new tester more like the one in the video so hopefully that will do the trick. It is aggravating not being able to find a leak.

thx alot

This video was perfect I am trying to figure out how to make my own leak down tester and this video really helped me understand how to do it myself. Very clear, and well to the point. Thanks so much for making a video a rookie could easily digest and walk away from not feeling so much like a rookie. I am not sure I have taps large enough for those threadings but I will either pick one up or just use JB weld as we are only dealing with max 7 PSI. Should be able to rig something up like that all half assed and still get the job done because of such low pressures. My biggest question for me right now is how I am going to administer the air into the engine. I really like the hand pump but not sure I will find one locally although I'm sure harbor freight has something of that nature. A Schrader valve does seem kinda nice but also so does the hand pump. we shall see but regardless thank you for such a clear and to the point video. I ride old 2stroke mopeds. Most of mine are French motobecanes or Puchs from Austria. Cheers !

Install a ball valve right before the gauge. Shut it during test, and open to check if pressure is still the same after the 30 minutes.

Awesome demonstration! I just did a video on this and this video was in my recommended! You got a sub and a like from Themowermedic1 LLC!

That was a great informative video, can a guy use a smoke machine for this?

Good detail info on pressure/leak testing. I don't think it matters if the piston is at TDC or bdc air will fill the space either way.

I’m going to be doing a mild build on my Prebug Zuma and I loved seeing how easy it was to do a leak down test. I can only imagine the nightmare trying to tune that engine with those leaks lol. Also, what tool were you using to install your crank?

Awesome video! I was about to ask where we can get the t shirts but I see that you linked them already! What rear tire/tire size is that?

I'm retired two stroke mech I have used guages that leak and have found them to leak right at the joint between the connection and the the curved tube in twelded joint and if not there it may leak at the closed end where the linear grear connects to the curve tube which is called the stanktion tube those jopint are silver welded, you can just reweld them with oxy-acsetaline and 99% silver such that is used with AC systems. But be mindful about not over heating the brass stanktion tube it is very thin brass sheeting.

And I learned that if you go race speeds you will melt any jb weld or compound for sure for sure. And the oil will always make it not as solid as it should be which makes it detoriate. Can only do that to sell it or like an engine plug bolt. Stator area. Back of motor type deal.

If you were to pressurize the water jacket with the same pressure as the cylinder, if there was a leak between them the pressure would not change. So for that engine, block off one coolant port (hose and plug) and put a "T" in your pressure line and pressurize the other one similar to how you pressurize the intake. Then compare the leakdown with the coolant under pressure and not under pressure. If there is more leakdown with the latter, then it's the head. However, keep in mind the cylinder head gets combustion pressure so it's a _LOT_ more than 7 PSI. So passing a low pressure test does not mean it will pass a running pressure on it.

I take a lawn mower spark plug and crack the insulator and drill and press a small metal spacer from the hardware store on to the empty spark plug housing weld it into place then cut the insert part of a tire valve stem and polish it or glue it and press it into the housing. I have a pressure port that’s a short spark plug. Works on most engines.

This video has been so handy. I’m still using the method as I’m still getting a drop, but it identified a crack which I’ve now repaired. One question, I’m loosing a bit at the carb manifold, so need to refine the connection I’ve made, however as the air goes in, should the reeds not prevent air coming back in that direction??? If so, it means my reeds are leaking and don’t seal.

Hi Brent. Great video (once again) I have all the stuff coming from Amazon as I type. I just replaced the crank bearings in my RH 50 and had 2 issues... 1 the bearings were very stiff. you could turn the crank by hand but it wasn't as easy as I thought it should have been... It started right up and ran fine but made a whirring noise when you came off the throttle... The cases had a paper gasket (that I did not replace) I just used Honda Bond... Could not using a gasket give me clearance issues? As well as a leak? I'll let you know what I find on the pressure test...

Just an easy tip. I use a boat hull plug to seal the exhaust port for pressure testing. Available at Walmart or any boat shop

Hi Brent, Since you like building, modification, assembling and disassemble engines. Have you ever thought of installing a pressure gauge to the crank to see how much pressure is in there. That will be interesting.

2022 Triumph Scrambler, 1200XC with an oil leak at the drive sprocket shaft. I noticed this leak in the showroom before I even bought the bike. Where are the pressure relief valves on this particular motorcycle? I’ve also noticed oil seeping from the gasket to the cover on the bottom of the engine. Clearly, this must to be excessive, crank case pressure. What could possibly be blocked or malfunctioning on a brand new motorcycle that would cause an oil leak because of access crank case pressure ? Could a bad PCV valve cause this excessive crank case pressure ? If not, what could be malfunctioning or blocked?

Will it work with radiator attached to see if i had blown gasket or not?. I'm assuming water on radiator will rise or bubbling if i had a leak

Hi Brent, After assembly of cases and engine. How long after to do the leak down test? I am thinking of gaskets, gasket maker, silicon gaskets and so on.

"Reapply JB Weld"...LOL! JB Weld is to get you home from the trail. Grind it out and weld it up so it's permanent. Some useful info here but feel this video could have been condensed to about 10-15 minutes. Otherwise good info. Thanks.

Just wondering, could you use a tyre foot pump with a gauge and a made up fitting to suit?

Is there a way to do this test with the carburetor attached to make sure no leaks there? Would I just plug as you did and apply the air beginning at the air intake port of the carb?

Where do I get the driver's license I had the same exact motor same problem

do you reccomend i get a better crankshaft with a glixal 80cc big bore kit?

When your applying pressure does that push out reed valves? Would it damage them?

Cool rims what are they off ?

The Is this way to find that airleak if you have any problems you submerge it in a bucket of water The breather owes that comes out of the transmission You have that above the water

I could not jet my yz after new top end turns out my ignition side crank seal was toast

just add a check valve to the end to separate the engine from the tester

how do you know if your reeds are leaking

i just need a pressure tester for my pressure tester

I USE PERMATEX COPPER SPRAY A GASKET ON ALL THE GASKETS ON ENGINE ASSY..THEN WHEN I INSTALL THE CYLINDER I COAT THE CYLINDER WITH LUCAS BREAK-IN 0IL...RETIRED LARRY. ...

So would a ten psi fuel pump and vacuum tester work

Hello! Should reed valves hold any pressure? I made a leak test device inspired on yours (filled through the sparkplug) but I haven´t covered the intake, assuming the reed valves should hold some pressure. They don´t. And they are brand new Polini, and have no light leaks whatsoever.

Гуд джоб !

most likely the gauge is fine the check balls inside the bulb is the more likely culprit of the leak

why cant you just get the piston so its just before tdc, hold the flywheel, and pump the air in ?

Would it be possible to, theoretically, build pressure from the back of the exhaust, or is that asking for too much trouble? I suspect that I may have leaks from all around my hoses going to the carb, so I wanted to build pressure without removing it in the first place. Taking the exhaust off and using a plate from the exhaust side of the cylinder could work, but I was wondering if I could just get away without taking things apart. Thanks!

I'm not an native english speaker so you must have say it in the video but I couldn't understand. I prefer read/write. What happend if a 2 stroke engine leak air like your ? Less power ? More air are coming in ? Possible failure ? Thank you very much.

That's jb weld for you

Where do I get the rubber seals from I mean

PLEASE READ! If you plug one coolent port and semi plug the other W/ a small pinhole leak in the other you can apply your liquid to the hole on the pinhole plug it will bubble and tell you if any leak is present! GOD BLESS YOU! Thank You!!!! 💪🇺🇸🏁

Seems like kickstart shaft is the only weak point everything else exact position while kickstart shaft and spring kinda moves

Will J.B.Weld be strong enough for REPAIR??? RETIRED LARRY...